A continuing trend in integrated circuit device is the steady shrinkage of device dimensions. This shrinkage has proceeded on a fairly steady exponential curve for many years. The minimum patterned dimension is commonly referred to as the “critical dimension.” With conventional MOS technology, as the critical dimension shrinks, the gate oxide becomes thinner, the diffusions become shallower, and the transistor minimum channel length becomes smaller.
As the size of contact and via holes shrink, it has been necessary to use thinner photo-resist. This, in turn, means that a less aggressive oxide etch must be used, so that the photo-resist is not destroyed in the process. Additionally, when using thinner resist, the contact or via etch must have greater selectivity to resist, and this requirement is approaching the limitation of current etches.
As the limits of current lithographic techniques are reached, methods of attaining smaller sized structures have been explored. It is known to use sidewall spacers on masking structures as a means to attain sub-lithographic dimensions. However, this technique has been limited by the fact that the available materials for forming sidewalls require high temperature processing, and their use is thus incompatible with the presence of photo-resist.
It has also been disclosed to use organic materials such as parylene and plasma deposited polymers such as Teflon®, for disposable spacers. One set of processes uses disposable organic spacers made from such compounds in combination with a shallow-trench-isolation pattern, to promote rounding of the trench edge and protection of this edge during subsequent etches. Another set of processes uses disposable organic spacers made from such compounds to decrease the size of contact holes and vias. Since the lithographic size of the hole in the photo-resist can be increased for a given end result, this allows a thicker photo-resist to be used, with the consequent ability to use a more aggressive oxide etch, white decreasing etch selectivity limits. Another set of processes uses disposable organic sidewall spacers made from the compounds listed above in combination with photo-resist to permit alteration of the line-to-space ratio, and to create sub-lithographic structures.
A need exists in the art for a method to form sidewall spacers from a compound which can be deposited using vapor deposition techniques and which can easily be removed during the fabrication process of semiconductor devices.